[TypeScript] as const, force immutability for Object type

Unlike JavaScript's 

const

 variable declarations, TypeScript allows you to create fully immutable types. In this lesson, we learn how to create immutable types in TypeScript with the help of 

as const

const user = {
    name: 'xxx',
    education: {
        degree: 'MSc'
    }
} as const
const users = [
    'a',
    'b'
] as const
user.education.degree = "BSc"
users.push('c')